Elevator door and bridge



June 14, 1949. 'E. E;ALIEXANDER 2,473,125

' ELEVATOR noon AND BRIDGE Fil ed April 17, 1946 2 Shee'tsShee 1 A INVENTOR. 'fzia 6'. MW

BY d/jh June 14, 1949; EALEXANDER I Y 2,473,125 Q ELEVATOR DOOR AND I BRIDGE Patented June 14, 1949 UNITED STATES PATENT OFFICE ELEVATOR DOOR AND BRIDGE Elisha E. Alexander, Chicago, Ill.

Application April 17, 1946, Serial No. 662,782

1 Claim. 1

My invention pertains to elevator doors and more specifically to a bridge actuated with the elevator door for spanning a gap normally existing between the elevator floor and a corresponding platform or building floor.

In recent years the loads handled by elevators have increased markedly, necessitating in some instances the use of power appliances such as motors to actuate associated devices such as elevator doors in order to reduce the time and effort of operation. These motor drives often employ slip clutches to prevent damage to the operating parts of the elevator door assembly by overrunning or by the accidental imposition of obstructions. While this arrangement is economical, considerable difficulty has been encountered in its use since marked variations in load cause undesirable slipping of the clutch. This often occurs where a hinged bridge is actuated directly or indirectly through the motor.

It is therefore a primary object of my invention to provide an elevator door and bridge assembly in which the force required for operation is substantially constant thereby permitting the satisfactory use of motor driven slip clutches for door actuation.

Other objects of my invention include the provision of a novel bridge operating clip to reduce the effort required for lowering the bridge and reduce the wear on the bridge member. These and other objects of my invention will become apparent from the following specification and from the drawings in which Figure 1 is a partially sectioned isometric view indicating the general arrangement of the parts of my invention;

Figure 2 is a fragmentary isometric view showing the engagement of the bridge and clip when the bridge is in raised position;

Figure 3 is a fragmentary isometric view showing the position of the clip and bridge when the bridge is in lowered position;

Figure 4 is an end view showing the arrangement of parts when the bridge is lowered;

Figure 5 is a fragmentary end section showing the position of the counterweight when the bridge is lowered;

Figure 6 is similar to Figure 5 but indicates the position of the counterweight when the bridge is raised;

Figure 7 is a detailed elevation of the counterweight;

Figure 8 is a cross section taken along the lines 8-8 of Figure '7; and a Figure 9 is a diagrammatic cross section of 2 the bridge and clip illustrating the action of the clip.

Many types of elevator doors are in common use today and may open horizontally or vertically. In compliance with R. S. 4888, I have selected a horizontally split elevator door to illustrate my invention, but it is not to be understood that I intend to limit myself to this specific embodiment of my invention or to the other specific details described herein except in so far as defined by the appended claim.

Referring to Figure 1, an upper door 2! and lower door 22 are provided to expose an elevator shaft and are adapted to be parted by vertical movement. Guides 23 attached to the building wall 24 are provided to define the path of the doors 2| and 22. A bridge 25 is attached to a door sill 21 by hinges 28 and extends across the door opening. The bridge 26 may have either a flat or somewhat rounded central section and beveled edges, the width of the bridge being suflicient to extend outwardly when in lowered position beyond the sill 2'! into contact with the floor of an elevator. Obviously the bridge 26 must be of substantial construction since its purpose is to support a load being transferred into or out of the elevator.

The doors 2| and 22 are interconnected by cable or rope 29 which extends around pulleys 3| and 32 attached to the building wall 24. The pulley 3| may be an idler pulley and the pulley 32 driven by a slip clutch 33 which is actuated by a motor 34. The slip clultch 33 may be of ordinary construction wherein a pair of friction plates are held together under spring pressure sufficient to permit the movement of a load less than a predetermined figure. Thus, as the doors reach their open position, one of the plates of the clutch 33 will be stopped while the other may continue to rotate. Similar action will occur if the doors should accidentally strike an unyielding obstruction or if the effort required to open the doors is suddenly increased. In conventional constructions, a sudden increase in load is often encountered at the time the bridge is moved by The supported in a raised position by cables or chains 39 secured to the free edge of the bridge and in its raised position is inclined towards the door but not in contact therewith. As the door is opened, the ears 3'! on the clips 36 engage the bridge 26 along the edges of the slots 38 thereby moving the door downwardly over the lower door 22 into lowered position.

The cable 39 is guided from an inclined to a vertical course bya guide pulley 42 attached to the building wall 24. The cable extends upwardly around a pulley 43 also attached to the building wall and then downwardly to a weight 44 to which may be attached a clevis 45. Since the weight required to balance the bridge varies according to the position of the bridge, it is obvious that one weight moving, in a verticalpath will never truly counterbalance the bridge except in one position.

In order to substantially counterbalance the bridge in raised, lowered, or any intermediate position, I provide a series of weights interconnected' by a: lost motion linkage and arranged in such manner that only the first weight is efiective as a counterbalance for the bridge while the bridge isstarting itsmovement from a raised to a lowered position. As the moment of the bridge about its hinges increases as the bridge moves from raised to lowered position, the lost motion linkage connects the next weight in the series with the first weight thereby increasing the effective weight of the counterweight and compensating for the increased bridge moment.

While obviously various forms of lost motion linkages can. be employed, I have illustrated one highly satisfactory type comprising a pair of rods 4! extending upwardly through openings 48 in the first weight 44. The rods 47 ar rigidly attached to-a' second weight 49- and have heads formed on the upper end which is a substantial distance above the upper surface of the first.

weight 44.. Resilient means such as springs 52- may be interposed between the head 5| and the upper surface of the first weight 44 and also in between the lower surface of the first weight 44' and the upper surface of. the second weight 49. A similar rod 53 is attached to athird weight 54 and extends upwardly through an opening 56 in: the second weight 49 terminating above the upper surfaceof theweight 49 in a head 51. A spring 58 or other resilient means is interposed between the head 51 and the upper surface of.

the Weight 49' and between the lower surface of. the weight 49 and. the upper surface of the weight 54. An opening 59 is formed in the lower surface of the. first weight 44' to receive theportion of the rod 53 which projects upwardly beyond the second weight 49. A cushion spring 6tmay be attached to the base of the third weight 54 and supports the weight resiliently against a stop 63 when the bridge is in. raised position. The weights 44, 49 and 54 may suit-- ably be generally rectangular in shape and are guided. in. their movement by vertical guides. 64 attached to. the building wall 24 adjacent the elevator.

As an elevator reaches the: level of the sill. 21,

the. motor 34 may be started either automatically orby the:- elevator operator thereby actuating the slip clutch 33 and the driving pulley 32 which causes-the elevator doors 2| and 22 to open. The-lower door 22: carrying the clips 35'c0ntinues its downward movement until the ears 3'! on theclips 35 contact the raised bridge 26; The ears 3! slidably engage the bridge ad,-

4 jacent the sides of the slot 38 and force the bridge from a raised to a lowered position.

It should be noted that the action of my clip 36 varies markedly from that of an ordinary right angle clip in that by the cooperative action of the slottedsill and the ears on the clip, a much shorter clip can be used without sacrificing leverage since the ears 3! engage the sill adjacent its free edg and continue in contact with the sill until'the bridge is completely lowered. This not only minimizes the shock imparted to the slip clutch 33 but also provides the maximum starting leverage obtainable without the necessity of a long and heavy clip. Furthermore, the wear on the bridge 25 occasioned by the frictional engagement of the bridge with the clip is distributed along an extended area instead of being concentrated at one point as is the case with conventional clips.

As the clip 36 forces the bridge 26 downwardly, the motion of the bridge is transmitted by the cable or chain 39 to the first weight 44. The weight 44 rises in the guide 64 until the upper surface of the weight engages the rods 41, the distance of travel of the weight 44 being preferably such that the second weight 49 will be moved by the rods 41 at the time the moment of the bridge about its hinges becomes sufilciently great to substantially exceed the counterbalancing moment exerted by the effective mass ofthe first weight 44. As the second weight 49 is drawn upwardly by the rods 41' and the cable 39, it will engage the head 51 on the rod 53 thereby moving the third weight 54. Therefore, as the bridge 26 is approaching its lowered position, when its moment about its hinges 28 is the greatest, all of the weights of the counterweight will be effective to counterbalance its. load. This not only reduces the efiort required to start the bridge in its downward path, but assists in the closing action.

As the doors 2|- and 22 are closed by actuation of the motor 34, the lower door 22 moves the bridge 26 upwardly. This lowers the third weight 54 into contact with the stop 53 and as the bridge continues to rise, the second weight 49 will come to rest on the resilient member 53 interposed between the weights 49 and 54, and as the bridge 26 reaches its raised position, the first weight 44 will be substantially in contact with the second weightv 49 and resiliently supported by the springs 52. The length of the cable 49 is selected to support the bridge 25 in a raised position out of contact with the lower door 22 but inclined at an angle to permit engagement with the clips 36, the weight of the first counterweight being just sufficient to maintain the bridge in this position.

The number of weights employed need not be limited specifically to three. Any desired number can be employed with suitable linkages between the various weights of the series to obtain' smoother operation. Furthermore, my invention is applicable to manually operated elevator door and bridgev mechanisms, since the effortless operation and reduction in shock imparted to such assemblies by my invention greatly reduces operator fatigue as'wellas time of operation.

I claim:

An elevator door and bridge assembly comprising a vertically movable door, a bridge horizontally pivoted at its inner margin adjacent the door and movable through; an angle of less than from a lowered substantially horizontal position" to. an-inclinedraisediposition, a clip carried by the door and movable, when the door is lowered, into a REFERENCES CITED slot in the bridge extending from the outer margin thereof inwardlv toward the pivoted margin 3 1 g ii fi are of record m the of the bridge, and a laterally extending ear on the clip adapted to ride upon the top surface of 5 UNITED S ATES PATENTS the bridge adjacent the slot as the door is lowered, Number Name D and to initially contact the bridge adjacent its 496 372 Ethridge May outer margin, whereby continued downward 1 5291122 Fischer 1925 movement of the door causes the ear of the clip 750,042 Hoover 1930 to smoothly cam the bridge to horizontal position 10 with minimum shock and use of power.

ELISHA E. ALEXANDER. 

